![Carbon metabolism in microalgae. Calvin cycle takes place in the chloroplasts (green circle); tricarboxylic acid cycle (TCA) occurs in the mitochondria (red circle); all the other metabolic pathways take place in the cytosol. Adapted from [23]](https://www.researchgate.net/profile/Lorenza-Ferro/publication/331487610/figure/fig1/AS:732665867141123@1551692563288/Carbon-metabolism-in-microalgae-Calvin-cycle-takes-place-in-the-chloroplasts-green_Q320.jpg)
![Photosynthetic light-response curve. α: slope of the curve, i.e. max light conversion efficiency; Pmax: maximal rate of photosynthesis; Ic: compensation irradiance, i.e. O2 balance between photosynthesis and respiration; Is: saturation irradiance; Ip: photoinhibition irradiance. Adapted from [20,29].](https://www.researchgate.net/profile/Lorenza-Ferro/publication/331487610/figure/fig2/AS:732665867161603@1551692563350/Photosynthetic-light-response-curve-a-slope-of-the-curve-ie-max-light-conversion_Q320.jpg)
![Schematic representation of a high rate algal pond (HRAP) for municipal wastewater treatment. Adapted from [81].](https://www.researchgate.net/profile/Lorenza-Ferro/publication/331487610/figure/fig3/AS:732665867141124@1551692563369/Schematic-representation-of-a-high-rate-algal-pond-HRAP-for-municipal-wastewater_Q320.jpg)
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Wastewater treatment and biomass generation by Nordic microalgae Growth in subarctic climate and microbial interactions
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Nordic native microalgal strains were isolated, genetically classified and tested for their ability to grow in municipal wastewater. Eight of the isolated strains could efficiently remove nitrogen and phosphate in less than two weeks. Two of these strains, Coelastrella sp. and Chlorella vulgaris, were found to have high biomass concentration and total lipid content; also two Desmodesmus sp. strains showed desirable traits for biofuel-feedstock, due to their fast growth rates and high oil content. The adaptation to subarctic climate was comparatively evaluated in three Nordic strains (C. vulgaris, Scenedesmus sp. and Desmodesmus sp.) and a collection strain (S. obliquus). Their growth performance, biomass composition and nutrients removal was investigated at standard (25°C) or low temperature (5°C), under continuous light at short photoperiod (3 h light, 25°C) or moderate winter conditions (6 h light, 15°C). Only the Nordic strains could grow and produce biomass at low temperature, and efficiently removed nitrogen and phosphate during both cold- and dark-stress. Phenotypic plasticity was observed in Scenedesmus and Desmodesmus under different growth conditions, adaptation to low temperature increased their carbohydrate content. Short photoperiod strongly reduced growth rates, biomass and storage compounds in all strains and induced flocculation in C. vulgaris, which, however, performed best under moderate winter conditions.
The symbiotic relationships between the Nordic microalga C. vulgaris and the naturally co-occurring bacterium Rhizobium sp. were investigated batchwise under photoautotrophic, heterotrophic and mixotrophic conditions, comparing the co-culture to the axenic cultures. The photoautotrophic algal growth in BG11 medium mainly supported Rhizobium activity in the co-culture, with no significant effects on C. vulgaris. In synthetic wastewater, a synergistic interaction only occurred under mixotrophic conditions, supported by CO2/O2 exchange and a lower pH in the culture, resulting in higher biomass and fatty acids content and more efficient wastewater treatment in the co-culture. Under heterotrophic conditions, the lower biomass production in the co-culture suggested a competition for nutrients, although nutrients removal remained efficient.
A pilot-scale high rate algal pond (HRAP) located in Northern Sweden was inoculated with the collection strain Scenedesmus dimorphus UTEX 417 and operated from spring to autumn. Using metabarcoding of 18S and 16S rRNA genes, the microbial diversity of eukaryotic and prokaryotic communities was revealed. S. dimorphus was initially stable in the culture, but other microalgal species later colonized the system, mainly due to parasitic infections and predation by zooplankton in summer. The main competitor algal species were Desmodesmus, Pseudocharaciopsis, Chlorella, Characium and Oocystis. Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria were the most abundant bacterial phyla in the HRAP. The structure of the microbial communities followed a seasonal variation and partially correlated to environmental factors such as light, temperature and nutrients concentrations.
Overall, these results contribute with new knowledge on the establishment and optimization of microalgal-based wastewater treatment systems coupled with biomass generation in Nordic areas. The use of native microalgal species is proposed as a potential strategy to overcome the limitations posed to algal cultivation in subarctic regions.
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... Figure 1. Carbon metabolism in microalgae (adopted from [44]). Different microalgal species have shown different tolerance limits and fixation rates (200-1000mg L -1 day -1 ) of CO2 present in flue gas, which was interestingly pronounced in mutated strains of the respective species [10,14,45,46]. ...
... Carbon metabolism in microalgae (adopted from[44]). ...
Increasing concentrations of carbon dioxide (CO2), one of the important greenhouse gases, due to combustion of fossil fuels, particularly burning coal, have become the major cause for global warming. As a consequence, many research programs on CO2 management (capture, storage, and sequestration) are being highlighted. Biological sequestration of CO2 by algae is gaining importance, as it makes use of the photosynthetic capability of these aquatic species to efficiently capture CO2 emitted from various industries and converting it into algal biomass as well as a wide range of metabolites such as polysaccharides, amino acids, fatty acids, pigments, and vitamins. In addition, their ability to thrive in rugged conditions such as seawater, contaminated lakes, and even in certain industrial wastewaters containing high organic and inorganic nutrients loads, has attracted the attention of researchers to integrate carbon capture and wastewater treatment. Algae offer a simple solution to tertiary treatments due to their nutrient removal efficiency, particularly inorganic nitrogen and phosphorus uptake. The algal–bacterial energy nexus is an important strategy capable of removing pollutants from wastewater in a synergistic manner. This review article highlights the mechanism involved in biological fixation of CO2 by microalgae, their cultivation systems, factors influencing algal cultivation in wastewater and CO2 uptake, the effect of co-cultivation of algae and bacteria in wastewater treatment systems, and challenges and opportunities.
... The carbon dioxide is absorbed from the atmosphere and stored as biomass which constitutes carbohydrates, lipids, and proteins. These biomolecules are synthesized from the intermediates such as Glyceraldehyde-3-phosphate, Ribulose-5-Phosphate, Phosphoglyceric acid, and NADPH generated in Calvin Cycle and Pentose Phosphate Pathway (Ferro, 2019). These intermediates of the two pathways facilitate various other metabolic reactions such as Kreb cycle, fatty acid synthesis, nucleic acid synthesis, etc. ...
Anthropogenic emissions of CO2 have reached a critical level and the global surface temperature is expected to rise by 1.5ºC between 2030 to 2050. To ameliorate the current global warming scenario, the research community has been struggling to find more economical and innovative solutions for carbon sequestration. Among such techniques, the use of microalgal species such as Chlorella sp., Dunaliella tertiolecta, Spirulina platensis, Desmodesmus sp., and Nannochloropsis sp., among others have shown high carbon tolerance capacity (10-100%) for establishing carbon capture, utilization and storage systems. To make microalgal-based carbon capture more economical, the microalgal biomass (~2 g/L) can be converted biofuels, pharmaceuticals and nutraceuticals through biorefinery approach with product yield in the range of 60-99.5%. Further, CRISPR-Cas9 has enabled the knockout of specific genes in microalgal species that can be used to generate low pH tolerant strains with high lipid production. Inspite of the emerging developments in pollution control by microalgae, only limited investigations are available on its economic aspects which indicate a production cost of ~$ 0.5-15/kg microalgal biomass. This review intends to summarize the advancements in different carbon sequestration techniques while highlighting their mechanisms and major research areas that need attention for economical microalgae-based carbon sequestration.
... Also, algae-based wastewater treatment bioreactors can be colonized by different organisms that act like grazers or parasites of the phytoplankton. For example, Ferro 2019 reports members of the groups Opisthokonta, Alveolata and Rhizaria, ciliates (Oligohymenophorea, Spirotrichea, Litostomatea classes), and amoeboids (Cercozoa phylum), but also multicellular organisms (Rotifera, Annelida, Nematoda phyla) accompanied by fungi (phyla of Cryptomycota, Chytridiomycota, Ascomycota) that negatively impacted the process in a prolonged operation of a HRAP [78]. In this regard, the control over the bacteria, protozoa, and macro grazers that could potentially affect the microalgal growth is nearly impossible. ...
Algae-based wastewater treatment technologies are promising green technologies with huge economical potential and environmental co-benefits. However, despite the immense research, work, and achievement, no publications were found wherein these technologies have been successfully applied in an operational environment for nitrogen and phosphorus removal of secondary treated effluent in municipal wastewater treatment plants. Based on a literature review and targeted comprehensive analysis, the paper seeks to identify the main reasons for this. The reliability (considering inlet wastewater quality variations, operating conditions and process control, algae harvesting method, and produced biomass) as well as the technology readiness level for five types of reactors are discussed. The review shows that the reactors with a higher level of control over the technological parameters are more reliable but algal post-treatment harvesting and additional costs are barriers for their deployment. The least reliable systems continue to be attractive for research due to the non-complex operation and relieved expenditure costs. The rotating biofilm systems are currently undertaking serious development due to their promising features. Among the remaining research gaps and challenges for all the reactor types are the identification of the optimal algal strains, establishment of technological parameters, overcoming seasonal variations in the effluent’s quality, and biomass harvesting.
... The presence of high organic compound loads in the wastes used as culture media to grow heterotrophic microalgae increases the risk for contamination by competitive heterotrophic bacteria and fungi, compromising the quality of the process and products if good laboratory practice is not followed [63]. For this reason, heterotrophic microalgae growth requires media sterilization, or, at least, sanitation, an energetic requirement that can account for 20-30% of the total production process costs. ...
In the last few decades, microalgae have attracted attention from the scientific community worldwide, being considered a promising feedstock for renewable energy production, as well as for a wide range of high value-added products such as pigments and poly-unsaturated fatty acids for pharmaceutical, nutraceutical, food, and cosmetic markets. Despite the investments in microalgae biotechnology to date, the major obstacle to its wide commercialization is the high cost of microalgal biomass production and expensive product extraction steps. One way to reduce the microalgae production costs is the use of low-cost feedstock for microalgae production. Some wastes contain organic and inorganic components that may serve as nutrients for algal growth, decreasing the culture media cost and, thus, the overall process costs. Most of the research studies on microalgae waste treatment use autotrophic and mixotrophic microalgae growth. Research on heterotrophic microalgae to treat wastes is still scarce, although this cultivation mode shows several benefits over the others, such as higher organic carbon load tolerance, intracellular products production, and stability in production all year round, regardless of the location and climate. In this review article, the use of heterotrophic microalgae to simultaneously treat wastes and produce high value-added bioproducts and biofuels will be discussed, critically analyzing the most recent research done in this area so far and envisioning the use of this approach to a commercial scale in the near future.
Decomposition models of solar irradiance estimate the magnitude of diffuse horizontal irradiance from global horizontal irradiance. These two radiation components are well known to be essential for predicting the performance of solar photovoltaic systems. In open-field agrivoltaic systems (i.e., the dual use of land for both agricultural activities and solar power conversion), cultivated crops receive unequal amounts of direct, diffuse, and reflected photosynthetically active radiation (PAR). These uneven amounts depend on where the crops are growing due to the non-homogenous shadings caused by the presence of the installed solar panels (above the crops or vertically mounted). It is known that, per unit of total PAR, diffuse PAR is more efficient for canopy photosynthesis than is direct PAR. For this reason, it is essential to estimate the diffuse PAR component when agrivoltaic systems are being assessed, in order to properly predict the crop yield. Since PAR is the electromagnetic radiation in the 400–700 nm waveband that can be used for photosynthesis by the crops, several stand-alone decomposition models typically used to split global horizontal irradiance are selected in this study to decompose PAR into direct and diffuse. These models are applied and validated in three locations in Sweden (Lanna, Hyltemossa and Norunda) using the coefficients stated on the models’ original publications and locally fitted coefficients. The results showed weaker performances in all stand-alone models for non-locally fitted coefficients (nRMSE ranging from 27% to 43%). However, performances improve with re-parameterization, with a highest nRMSE of 35.24% in Lanna. The Yang2 decomposition model is the best-performing one, with the lowest nRMSE of 23.75% in Norunda when applying re-estimated coefficients. Country level sets of coefficients for the best-performing models (Yang2 and Starke) are given after parameterization using combined data for all three locations in Sweden. These Sweden-fitted models are tested and show an nRMSE of 25.08% (Yang2) and 28.60% (Starke). These results can be used to perform estimations of the PAR diffuse component in Sweden wherever ground measurements are not available. The overall methodology can be similarly applied to other countries.
In recent decades, there has been a tremendous increase in fuel requirement all around the world. This has caused severe exploitation of conventional fuel resources leading to subsequent increase in the level of pollution owing to their consumption. There is a growing concern regarding exploration of alternate, safe sources of energy. Since the time immemorial, algae are known for producing a vast array of useful products, which has benefited the mankind. Algae also harbor high amount of biomolecules such as lipids and carbohydrates, which can be converted into biofuels. Therefore, algal biofuels have gained tremendous attention in past few years and several technologies related to algal biofuels have been developed. The major drawback in this area is the limited potential of algae to synthesize biomolecules to be converted into biofuels. Since, the demand of biofuels is very high and production is very low, therefore, genetic engineering technologies were explored to increase the yield of biofuels. In this chapter, we have discussed different types of biofuels produced from microalgae and recent genetic engineering-based studies employed for sustainable biofuel production.
The work is devoted to the study of technological processes corresponding to the requirements of the developing closed-loop economy, which will be based on the wide use of renewable resources, maximum recycling of secondary raw materials, with the transition from fossil fuels to renewable energy sources as one of the objectives. A study of the possibility of producing fatty acid esters from renewable raw materials of plant origin - microalgae Chlorella vulgaris - with the use of municipal wastewater was carried out. Approaches to the development of technologies of fatty acid esters production and promising ways to improve the key stages of such production are considered. It is shown that under certain conditions (temperature of 10-32 °С, illumination of 7-14 klx) municipal wastewater can be treated and at the same time serve as a nutrient medium in the process of cultivation of microalgae biomass with lipid content of 10-18% of dry matter. Depending on the conditions of cultivation, the cells of the Chlorella vulgaris IPPAS C-2 strain of microalgae reduce the concentration of ammonium cations, phosphate anions and total microbial number in municipal wastewater by 93 - 95% (wt.), 90 - 97% (wt.) and 86 - 95%, respectively. The influence of technological conditions of the process on the biomass growth rate and fatty acid composition of accumulated lipids is analyzed. It is experimentally established that triglycerides, O-dialkylmonoglycerides and fatty acids have the greatest inhibiting effect on the microflora of wastewater. Using Hansen solubility parameters, a system of polar and non-polar solvents consisting of ethanol and petroleum ether in the ratio of 1:2 (vol). was selected, which ensures the efficient conduct of the extraction process. The yield of fatty acid esters of КFAE = 45% was obtained in the course of transesterification reaction with the use of ethanol in the ratio with lipids 6:1 (mole) at the reaction temperature of 60 °C in the presence of an alkaline catalyst - sodium hydroxide (3% of the mass of lipids).
In order to investigate environmentally sustainable sources of organic carbon and nutrients, four Nordic green microalgal strains, Chlorella sorokiniana, Chlorella saccharophila, Chlorella vulgaris, and Coelastrella sp., were grown on a wood (Silver birch, Betula pendula) hydrolysate and dairy effluent mixture. The biomass and lipid production were analysed under mixotrophic, as well as two-stage mixotrophic/heterotrophic regimes. Of all of the species, Coelastrella sp. produced the most total lipids per dry weight (~40%) in the mixture of birch hydrolysate and dairy effluent without requiring nutrient (nitrogen, phosphorus, and potassium-NPK) supplementation. Overall, in the absence of NPK, the two-stage mixotrophic/heterotrophic cultivation enhanced the lipid concentration, but reduced the amount of biomass. Culturing microalgae in integrated waste streams under mixotrophic growth regimes is a promising approach for sustainable biofuel production, especially in regions with large seasonal variation in daylight, like northern Sweden. To the best of our knowledge, this is the first report of using a mixture of wood hydrolysate and dairy effluent for the growth and lipid production of microalgae in the literature.
We tested 37 photoautotrophic microalgal strains of various taxonomic positions for their heterotrophic growth on glucose. We showed that facultative heterotrophy was quite common among certain groups of green algae (Chlorellales or Sphaeropleales) and of Xanthophyceae, whereas it was completely absent from Eustigmatophyceae. For the first time, we found heterotrophy in some members of green algae (Botryosphaerella sudetica, Bracteacoccus sp., Dictyosphaerium spp., Lemmermannia sp., Parachlorella kessleri). Of the tested facultative heterotrophs, three strains, Scenedesmus sp., Dictyosphaerium chlorelloides, and Tribonema aequale, were selected to investigate, in detail, their mixotrophic growth and production of specific metabolites, carotenoids, exopolysaccharides, and eicosapentaenoic acid, respectively. Among them only T. aequale showed significantly higher production of the target compound, eicosapentaenoic acid, under the mixotrophic cultivation mode than photoautotrophically. Together with the ease of biomass harvest, Tribonema microalgae are therefore proposed as a possible source of high-quality ω-3 polyunsaturated fatty acids.
With a unique cell structure and clear genetic background, Chlamydomonas reinhardtii has become a model species for fundamental research on microalgae and lower plants. Genetic transformations in the nucleus and chloroplast and mitochondrial genomes of C. reinhardtii have been successfully developed. However, research of C. reinhardtii has mainly focused on physiology and molecular genetics and few studies investigating cultivation methods have been performed. Small scales, slow growth, and low yields from conventional photoautotrophic and mixotrophic cultures severely limit the further development and application of C. reinhardtii. This study sought to optimize and scale up the heterotrophic cultivation process for C. reinhardtii. Critical parameters in 500-mL shake flasks were optimized as follows: liquid volume of 150 mL, initial inoculation of 0.08 g L⁻¹, growth temperature of 30 °C, and shaking speed of 150 rpm. In addition, this study confirmed that, although C. reinhardtii can assimilate acetic acid for heterotrophic growth (optimum initial concentration of 80 mM), neither glucose nor glycerol can be the only carbon source. Nitrate, ammonia, and urea can be used as nitrogen sources for heterotrophic culture, while the optimal carbon and nitrogen ratio for heterotrophic culture was 40:1. Under optimal conditions, the C. reinhardtii biomass increased from 0.457 to 1.32 g L⁻¹. Furthermore, for the first time, heterotrophic cultures of C. reinhardtii were scaled up to 5-L and 50-L fermenters, in which the cell density reached 25.44 g L⁻¹ after 237 h, which is 2.82-fold higher than previously reported.
Algae are without doubt the most productive photosynthetic organisms on Earth; they are highly efficient in converting CO2 and nutrients into biomass. These abilities can be exploited by culturing microalgae from wastewater and flue gases for effective wastewater reclamation. Algae are known to remove nitrogen and phosphorus as well as several organic contaminants including pharmaceuticals from wastewater. Biomass production can even be enhanced by the addition of CO2 originating from flue gases. The algal biomass can then be used as a raw material to produce bioenergy; depending on its composition, various types of biofuels such as biodiesel, biogas, bioethanol, biobutanol or biohydrogen can be obtained. However, algal biomass generated in wastewater and flue gases also contains contaminants which, if not degraded, will end up in the ashes. In this review, the current knowledge on algal biomass production in wastewater and flue gases is summarized; special focus is given to the algal capacity to remove contaminants from wastewater and flue gases, and the consequences when converting this biomass into different types of biofuels.
Microalgal biomass is processed into products by two main process steps: 1) harvesting and dewatering; and 2) extraction, fractionation and conversion. The performance of unit operations for harvesting and dewatering is often expressed in qualitative terms, like “high energy consumption” and “low in operational cost”. Moreover, equipment is analysed as stand-alone unit operations, which do not interact in a chain of operations. This work concerns a quantitative techno-economic analysis of different large-scale harvesting and dewatering systems with focus on processing cost, energy consumption and resource recovery. Harvesting and dewatering are considered both as a single operation and as combinations of sequential operations. The economic evaluation shows that operational costs and energy consumption are in the range 0.5–2 €·kg− 1 algae and 0.2–5 kWh·kg− 1 of algae, respectively, for dilute solutions from open cultivation systems. Harvesting and dewatering of the dilute systems with flocculation results in the lowest energy requirement. However, due to required chemicals and loss of flocculants, these systems end at the same cost level as mechanical harvesting systems. For closed cultivation systems the operational costs decrease to 0.1–0.6 €·kg− 1 algae and the energy consumption to 0.1–0.7 kWh·kg− 1 algae. For all harvesting and dewatering systems, labour has a significant contribution to the total costs. The total costs can be reduced by a high level of automation, despite the higher associated investment costs. The analysis shows that a single step operation can be satisfactory if the operation reaches high biomass concentrations. Two-step operations, like pressure filtration followed by spiral plate technology or centrifugation, are attractive from an economic point of view, just as the operation chain of flocculation followed by membrane filtration and a finishing step with spiral plate technology or centrifugation.
The research on microalgal biodiesel is focused not only on getting the highest lipid productivity but also desired quality of lipid. The experiments were initially conducted on flask scale (1L) using acetate carbon source at different concentrations viz. 0.5, 2, 3 and 4 g L–1. The optimum concentration of acetate was considered for further experiments in two airlift photobioreactors (10 L) equipped separately with red and white LED lights. The feasibility index (FI) was derived to analyze the scalability of mixotrophic cultivation based on net carbon fixation in biomass per consumption of total organic carbon. The experimental strategy under mixotrophic mode of cultivation lowered the α-linolenic acid content of lipid by 60–80% as compared to autotrophic cultivation for Scenedesmus abundans species and yielded the highest biomass and lipid productivities, 59 ± 2 mg L–1d–1 and 17 ± 1.8 mg L–1d–1, respectively. The TOC, nitrate, and phosphate reduction rates were 74.6 ± 3.0 mg L–1 d–1, 11.5 ± 1.4 mg L–1 d–1, 9.6 ± 2.4 mg L–1 d–1 respectively. The significant change was observed in lipid compositions due to the scale, mode of cultivation, and light spectra. As compared to phototrophic cultivation, biodiesel obtained under mixotrophic cultivation only met standard biodiesel properties. The FI data showed that the mixotrophic cultivation was feasible on moderate concentrations of acetate (2–3 g L–1).
The concept of sustainable biodiesel production using microalgae has attracted a lot of attention as an emerging green energy technology. However, low algal biomass and lipid productivity hinder cost-effective biodiesel production. To overcome these problems, this study examined the effect of bacterial volatile compounds (VCs) on the growth and lipid production of microalga Chlorella vulgaris OW-01. The VCs of phycospheric bacteria including Hyphomonas sp., Rhizobium sp., and Sphingomonas sp. efficiently augmented algal biomass in a newly developed VCs experimental apparatus. Moreover, an apparent increase in total lipid content along with a 2.34-fold increase in productivity was observed in Hyphomonas sp. VCs-exposed algal biomass. Fatty acid methyl esters (FAME) composition also demonstrated that the algal biodiesel properties were somewhat modified by exposure to bacterial VCs. A LiOH filter-inducing CO 2-removed bacterial VCs (CRBVCs) also enhanced daily growth of microalgae, as compared to the control culture (aeration), indicating that CRBVC included growth-promoting volatiles. Of those factors, volatile indole was identified as a possible algal growth enhancing factor, and it showed a higher growth-promoting effect than dimethyl disulfide and dimethyl trisulfide. Based on these results, it is speculated that the use of bacterial VCs for algal cultivation is a promising future bioprocess for the algal biomass and biodiesel production.
Eight recently isolated microalgal species from Northern Sweden and the culture collection strain Scenedesmus obliquus RISE (UTEX 417) were tested for their ability to remove 19 pharmaceuticals from growth medium upon cultivation in short light path, flat panel photobioreactors. While the growth of one algal species, Chlorella sorokiniana B1-1, was completely inhibited by the addition of pharmaceuticals, and the one of Scenedesmus sp. B2-2 was strongly inhibited, the other algal strains grew well and produced biomass. In general, lipophilic compounds were removed highly efficient from the culture medium by the microalgae (> 70% in average within 2 days). The most lipophilic compounds Biperiden, Trihexyphenidyl, Clomipramine and Amitriptyline significantly accumulated in the biomass of most algal species, with a positive correlation between accumulation and their total biomass content. More persistent in the growth medium were hydrophilic compounds like Caffeine, Fluconazole, Trimetoprim, Codeine, Carbamazepin, Oxazepam and Tramadol, which were detected in amounts of above 60% in average after algal treatment. While Coelastrella sp. 3-4 and Coelastrum astroideum RW10 were most efficient to accumulate certain compounds in their biomass, two algae species, Chlorella vulgaris 13-1 and Chlorella saccharophila RNY, were not only highly efficient in removing all 19 pharmaceuticals from the growth medium within 12 days, at the same time only small amounts of these compounds accumulated in their biomass allowing its further use. Chlorella vulgaris 13-1 was able to remove most compounds within 6 days of growth, while Chlorella saccharophila RNY needed 8-10 days."Wild" Nordic microalgae therefore are able to remove active pharmaceutical ingredients, equally or more efficient than the investigated culture collection strain, thereby demonstrating their possible use in sustainable wastewater reclamation in Nordic conditions.
Many dinoflagellate cysts experience dormancy, a reversible state that prevents germination during unfavorable periods. Several of these species also cause harmful algal blooms (HABs), so a quantitative understanding of dormancy cycling is desired for better prediction and mitigation of bloom impacts. This study examines the effect of cold exposure on the duration of dormancy in Alexandrium catenella, a HAB dinoflagellate that causes paralytic shellfish poisoning (PSP). Mature, dormant cysts from Nauset Marsh (Cape Cod, MA USA) were stored at low but above freezing temperatures for up to six months. Dormancy status was then determined at regular intervals using a germination assay. Dormancy timing was variable among temperatures and was shorter in colder treatments, but the differences collapse when temperature and duration of storage are scaled by chilling-units (CU), a common horticultural predictor of plant and insect development in response to weather. Cysts within Nauset meet a well-defined chilling requirement by late January, after which they are poised to germinate with the onset of favorable conditions in spring. Cysts thus modulate their dormancy cycles in response to their temperature history, enhancing the potential for new blooms and improving this species' adaptability to both unseasonable weather and new habitats/climate regimes.
Microalgae have important potential in the bio-based industry. However, their light-utilization mechanisms are still not fully understood. Together with knowledge of their metabolic pathways and their responses in carbon partitioning to different primary metabolites (carbohydrates, lipids and proteins), this information is essential if their potential and profitability are to be better exploited. The first part of this review describes the techniques used for microalgae cultivation and the growth factors that determine their productivity, one of the most important factors in techno-economic assessment studies of microalgae production systems. In the second part, a closer look is taken at their chemical composition in relation to the biosynthesis of primary and secondary metabolites. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd